HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Cabrita, A. R. J. Articles by Gomes, E. Search for Related Content PubMed PubMed Citation Articles by Cabrita, A. R. J. Articles by Gomes, E.

Nitrogen Supplementation of Corn Silages. 2. Assessing Rumen Function Using Fatty Acid Profiles of Bovine Milk

A. R. J. Cabrita^*,,, A. J. M. Fonseca^*,, R. J. Dewhurst and E. Gomes

^* Centro de Estudos de Ciência Animal do Institutode Ciências e Tecnologias Agrárias e Agro-Alimentares,
Faculdade de Ciências, and
Instituto de Ciências Biomédicas de Abel Salazar, Universidade do Porto, Campus Agrário de Vairão, Rua Padre Armando Quintas,4485-661 Vairão VC, Portugal
Institute of Grassland and Environmental Research, Plas Gogerddan, Aberystwyth, Ceredigion SY23 3EB, UK

Corresponding author: A. R. J. Cabrita; e-mail: rita.cabrita{at}mail.icav.up.pt.

The effects of N supplementation strategies on milk fatty acid profiles of dairy cows and their use as a noninvasive technique to diagnose rumen function, and to guide protein feeding decisions on-farm were evaluated in three experiments. Each experiment was designed according to three 3 x 3 Latin squares with 9 Holstein cows receiving total mixed rations based on corn silage. Experiment 1 was designed to study effects of diets with different ratios of effective rumen-degradable protein (ERDP; g) to fermentable metabolizable energy (FME; j) providing, respectively, a large deficiency, a slight deficiency, and a slight excess in relation to the target level of 11 g of ERDP/MJ FME for lactating cows. Experiment 2 evaluated effects of different proportions of quickly and slowly rumen-degradable protein achieved by replacing soybean meal with urea in the concentrates (0, 0.5, and 1% urea for U0, U5, and U10, respectively). Experiment 3 investigated effects of synchronizing the availability of FME and ERDP in rumen by offering the protein-rich concentrate once or twice per day before the meal (corn silage, ryegrass hay, and energy-rich concentrate), or included in the total mixed ration. Milk fatty acid profiles were significantly affected by dietary N and carbohydrate supply. Principal component factor analysis provided a reasonable description of the data, clearly discriminating between fatty acids that are synthesized by different metabolic pathways. Several sources/pathways were distinguished: de novo synthesis in the mammary gland (short- and medium-chain fatty acids), ⁹-desaturase activity (monoenoic fatty acids), direct absorption from the blood stream (long-chain fatty acids), and de novo synthesis by the rumen microbial populations (odd-chain fatty acids). Discriminant canonical analysis showed that milk odd-chain fatty acids had a higher ability to discriminate between diets than even-chain fatty acids. The anteiso C_15:0 increased in line with increasing sugar supply, and C_17:0 appears to be a marker of protein deficiency. Additionally, iso C_17:0 and anteiso C_17:0 were associated with the NDF and CP contents of diets. The results suggests that milk odd-chain fatty acids have the potential to be used as a noninvasive technique to assess rumen function in terms of microbial populations, substrates and interactions.

Key Words: bovine milk fatty acid profile • nitrogen supplementation • rumen function

Abbreviation key: D1 = protein-rich concentrate fed once a day before the a.m. meal, D2 = protein-rich concentrate fed twice a day before both meals, DU = protein-rich concentrate given with the basal diet, ERDP = effective rumen-degradable protein, FME = fermentable metabolizable energy, QDP = quickly rumen-degradable protein, RH = diet with a slight excess of ERDP in relation to FME, RL = diet with a large deficiency of ERDP in relation to FME, RM = diet with a slight deficiency of ERDP in relation to FME, SDP = slowly rumen-degradable protein, U0 = concentrate with 0% urea, U5 = concentrate with 0.5% urea, U10 = concentrate with 1% urea

This article has been cited by other articles:

				M. Craninx, A. Steen, H. Van Laar, T. Van Nespen, J. Martin-Tereso, B. De Baets, and V. Fievez Effect of Lactation Stage on the Odd- and Branched-Chain Milk Fatty Acids of Dairy Cattle Under Grazing and Indoor Conditions J Dairy Sci, July 1, 2008; 91(7): 2662 - 2677. [Abstract] [Full Text] [PDF]

				O. A. Rego, S. M. M. Regalo, H. J. D. Rosa, S. P. Alves, A. E. S. Borba, R. J. B. Bessa, A. R. J. Cabrita, and A. J. M. Fonseca Effects of Grass Silage and Soybean Meal Supplementation on Milk Production and Milk Fatty Acid Profiles of Grazing Dairy Cows J Dairy Sci, July 1, 2008; 91(7): 2736 - 2743. [Abstract] [Full Text] [PDF]

				A. R. J. Cabrita, R. J. B. Bessa, S. P. Alves, R. J. Dewhurst, and A. J. M. Fonseca Effects of Dietary Protein and Starch on Intake, Milk Production, and Milk Fatty Acid Profiles of Dairy Cows Fed Corn Silage-Based Diets J Dairy Sci, March 1, 2007; 90(3): 1429 - 1439. [Abstract] [Full Text] [PDF]

				E. J. Kim, R. Sanderson, M. S. Dhanoa, and R. J. Dewhurst Fatty Acid Profiles Associated with Microbial Colonization of Freshly Ingested Grass and Rumen Biohydrogenation J Dairy Sci, September 1, 2005; 88(9): 3220 - 3230. [Abstract] [Full Text] [PDF]

				B. Vlaeminck, C. Dufour, A. M. van Vuuren, A. R. J. Cabrita, R. J. Dewhurst, D. Demeyer, and V. Fievez Use of Odd and Branched-Chain Fatty Acids in Rumen Contents and Milk as a Potential Microbial Marker J Dairy Sci, March 1, 2005; 88(3): 1031 - 1042. [Abstract] [Full Text] [PDF]